Low-temperature, flexible, 0-3 composite piezoelectric materials can decrease the size, cost, and complexity of high-frequency acoustic devices on temperature sensitive substrates such as those in catheter based ultrasonic devices and acoustooptic sensors. In this paper, the application of low-temperature 0-3 connected composite thick films in flexible, non-planar, high frequency ultrasonic devices is reported. A flexible high-frequency ultrasound transducer and an acousto-optic radio-frequency (RF) field sensor are demonstrated utilizing PZT-based composite thick films. Flexible composite films have been fabricated with thicknesses between 20-100μm utilizing screen-printing, stencil-printing, and dip-coating techniques. Composite films' piezoelectric d 33 coefficient is measured, with results between 35-43 pC/N. Ultrasonic transducers utilizing these films demonstrate broadband acoustic response. A composite transducer is fabricated on flexible polyimide and wrapped around a 3mm catheter. Pulse-echo experiments demonstrate viability of these films as both as an actuator and a sensor in flexible devices. The composite material is further dip-coated onto an optical fiber Bragg grating to form a flexible acousto-optic RF field sensor. The sensor demonstrates RF field sensing in the 20-130 MHz range. The results from these experiments indicate significant potential for future flexible, high frequency ultrasonic devices utilizing low temperature 0-3 composite piezoelectric materials on temperature sensitive substrates.